Internal combustion engines (ICE's) are controlled based on a manifold absolute pressure (MAP) and mass air flow (MAF) signals that are generated by MAP and MAF sensors, respectively. A controller controls emissions and engine performance characteristics of the ICE based on the MAP and MAF signals. For example, critical engine parameters, such as air-to-fuel (A/F) ratio, can be adjusted by knowing the mass of air available for combustion.
MAF sensors are commercially available and have been used with ICE's to provide the required MAF information. MAF sensors, however, are relatively expensive as compared to other sensors implemented with the ICE. Therefore, alternative techniques for determining MAF into the ICE have developed. Two conventional techniques include a speed density technique and a throttle position technique. The speed density technique determines MAF based on MAP, engine speed and intake air temperature. The throttle position technique determines MAF based on throttle position and engine speed.
Although the conventional techniques eliminate the need for a MAF sensor, they are less accurate than desired. These inaccuracies result from an incorrect estimation of MAF during throttle transient conditions. During throttle transient conditions, a finite amount of time is required to calculate MAF and adjust fuel input. MAF can change dramatically due to the dynamic nature of the ICE during this time. Even during static conditions, the conventional techniques result in cycle-to-cycle measurement variations. More specifically, air flow pulsations that occur as the ICE draws air into the cylinders and delays in processing sensor information result in such cycle-to-cycle variations.